Sarcasm or gasboard: not a hidden choice presented to diners in Sweden at the annual Monty Python Ball
Explanation
Sarcasm or gasboard = contains SM OR GASBOARD
not a = remove an A to get SMORGASBORD
hidden = indicates that the answer is hidden in the foregoing text
choice presented to diners in Sweden etc = definition
Some of you may remember the gasboard sketch, but if you don't you'll need to fill in an R16 before I can tell you about it.